Cascade Range Current Updates
August 2008

Cascade Range Volcanoes
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

NOTICE: Mount St. Helens has been at Volcano Alert Level NORMAL and Aviation Color Code GREEN for the past month; therefore, we are migrating from a Mount St. Helens weekly update to a Cascade Range weekly update. As long as all Cascade Range volcanoes are at Normal and Green, we will continue to issue Cascade Range weekly updates. If a Cascade Range volcano shows signs of unrest, we will issue an update for that particular volcano.

Activity Update: All volcanoes in the Cascade Range are at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry Volcano, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

Recent Observations: Volcano seismicity at Mount St. Helens and elsewhere has remained quiet. Several stations on Mount Rainier (RCM (Camp Muir) in particular) have been noisy off and on since Sunday as winds from several passing storm systems have buffeted the upper elevations of the volcano. CVO crews were in the field at Mount St. Helens, Three Sisters, and Crater Lake this week for site assessments, repairs to existing monitoring stations, deformation surveys, and/or geological studies.

Cascade Range Volcanoes
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

NOTICE: Mount St. Helens has been at Volcano Alert Level NORMAL and Aviation Color Code GREEN for the past month; therefore, we are migrating from a Mount St. Helens weekly update to a Cascade Range weekly update. As long as all Cascade Range volcanoes are at Normal and Green, we will continue to issue Cascade Range weekly updates. If a Cascade Range volcano shows signs of unrest, we will issue an update for that particular volcano.

Activity Update: All volcanoes in the Cascade Range are at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry Volcano, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

Recent Observations: Volcano seismicity at Mount St. Helens has remained quiet, although several seismometers near Crater Glacier are recording small rock fall events and 'ice quakes' resulting from glacier movement. Microwave links to the SEPT and VAULT seismic stations at Mount St. Helens were lost on Monday as a result of lightning strikes. Repairs were made and links were restored on Thursday. A field crew is at Three Sisters volcano this week, conducting deformation monitoring using GPS and leveling methods.

Cascade Range Volcanoes
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

NOTICE: Mount St. Helens has been at Volcano Alert Level NORMAL and Aviation Color Code GREEN for the past month; therefore, we are migrating from a Mount St. Helens weekly update to a Cascade Range weekly update. As long as all Cascade Range volcanoes are at Normal and Green, we will continue to issue Cascade Range weekly updates. If a Cascade Range volcano shows signs of unrest, we will issue an update for that particular volcano.

Activity Update: All volcanoes in the Cascade Range are at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry Volcano, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

Recent Observations: The swarm of small, shallow earthquakes between Mount Shasta and Medicine Lake volcanoes that started on August 7 has stopped. The location and character of these earthquakes were consistent with a tectonic (non-volcanic) origin. However, because the swarm occurred in an area of scattered volcanic vents, we will continue to monitor the area closely. Volcano seismicity at Mount St. Helens has remained quiet, although several seismometers near Crater Glacier are recording small 'ice quakes' resulting from glacier movement. At Mount St. Helens this week, field crews performed maintenance on seismic stations and deployed targets for precision calibration of aerial photographs used in monitoring the crater. Hot, dry conditions and high winds have resulted in intermittently noticeable clouds of blowing ash within the crater and just above the crater rim, which could continue under current weather conditions.

Cascade Range Volcanoes
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

NOTICE: Mount St. Helens has been at Volcano Alert Level NORMAL and Aviation Color Code GREEN for the past month; therefore, we are migrating from a Mount St. Helens weekly update to a Cascade Range weekly update. As long as all Cascade Range volcanoes are at Normal and Green, we will continue to issue Cascade Range weekly updates. If a Cascade Range volcano shows signs of unrest, we will issue an update for that particular volcano.

Activity Update: All volcanoes in the Cascade Range are at normal levels of background seismicity. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State; Mount Hood, Mount Jefferson, Three Sisters, Newberry Volcano, and Crater Lake, in Oregon; and Medicine Lake, Mount Shasta, and Lassen Peak in northern California.

Recent Observations: A swarm of small, shallow earthquakes between Mount Shasta and Medicine Lake volcanoes has been ongoing since Thursday, 7 August. The sequence began with a M2.5 at 08:27 PDT on August 7, and included a M3.5 earthquake followed by a number of smaller earthquakes over the past 24 hours, including several M>2 earthquakes this morning (8 August). Earthquake epicenters are clustered near the trace of several NNW-trending regional faults and are located ~8 miles SE of the locus of the June-August 1978 Stevens Pass swarm, which included three M>4 earthquakes. The location and character of the 2008 earthquakes are consistent with a tectonic (non-volcanic) origin for the swarm. However, because the swarm is occurring in an area of scattered volcanic vents, we will continue to monitor the swarm closely and will issue updates if the situation warrants.

MOUNT ST. HELENS VOLCANO (CAVW#1201-05-)
46.20°N 122.18°W, Summit Elevation 8363 ft (2549 m)
Volcano Alert Level: NORMAL
Aviation Color Code: GREEN

The 40-month-long lava-dome eruption of Mount St. Helens that began in autumn 2004 ended in late January of this year. Earthquakes, volcanic gas emissions, and ground deformation are all at pre-eruptive background levels. The alert level and aviation color code were reduced to NORMAL/GREEN on July 10, 2008, following five months with no sign of renewed activity.

Even with the end of lava dome growth, some hazards persist. The new lava dome remains hot in places and capable of producing small hot avalanches or minor explosions that could dust areas with ash up to tens of miles downwind. Rock fall from the crater walls can produce clouds of dust that rise above the crater rim, especially during dry, windy days, as has happened in the past. Also, heavy rainfall or rapid snowmelt can send small debris flows onto the Pumice Plain north of the crater.

Recent observations: This week field crews made repairs to monitoring equipment, deployed photo targets for geodetic control points, continued tracking northward advance of Crater Glacier, and mapped geology on the volcano's flank. Scientists from the Cascades Volcano Observatory continue to monitor the volcano remotely. The past week's seismic record is dominated by rockfalls in the crater and glacier quakes caused by motion of the ice.